A multicarrier transmission system can effectively suppress multipath fading, and achieves high-speed data transmission, in addition, the implementation is simple and spectrum efficiency is high. For example, an orthogonal frequency-division multiplexing (Orthogonal frequency-division multiplexing, abbreviated as OFDM) technology. In a multicarrier system, a frequency selective fading channel is divided into several flat fading subcarriers orthogonal to each other; a spectrum adaptive function can be achieved by simply setting some subcarriers to be zero according to a dynamic change of the spectrum to make these subcarriers not transmit data, and therefore, multicarrier transmission has become the most promising physical layer transmission technology in dynamic spectrum sharing (dynamic spectrum sharing, abbreviated as DSS) and cognitive radio (Cognitive Radio).
Specific implementation modes of the multicarrier transmission system include, but not limited to, an OFDM system, a filter-bank based multicarrier (Filter-bank Based Multicarrier, abbreviated as FBMC), multicarrier code-division-multiple-access (Multicarrier Code-Division-Multiple-Access, abbreviated as MC-CDMA), and etc., and these techniques have a common feature of modulating and demodulating multicarrier signals based on discrete Fourier transform (Discrete Fourier Transform, DFT). According to the sampling theorem, the spectrum of a digital signal is periodic, this may cause frequency spectrum aliasing and thus may seriously affect the performance; therefore, in a practical multicarrier system, virtual subcarriers are set at two edges of a sampling bandwidth of a baseband signal, and the virtual subcarriers do not transmit signals. For example, FIG. 1 is a schematic diagram of configuring subcarriers in an OFDM system in the prior art, a system sampling frequency (i.e., a sampling bandwidth of a baseband signal) is greater than a signal transmission bandwidth, there are guard subcarriers, data subcarriers, DC subcarriers and pilot subcarriers in the signal transmission bandwidth, and the spectrum width occupied by the virtual subcarriers is approximately the sampling bandwidth minus the signal transmission bandwidth.
All the current multicarrier systems are premised on a static frequency spectrum scenario, that is, the adopted signal transmission bandwidth is pre-divided and fixed. When the system is designed and the product is implemented, the number and the locations of virtual subcarriers have been solidified, and thereby it is difficult to apply in a dynamic frequency spectrum scenario.